U.S. Pat. No. 6,254,355 describes an impedance pump which causes a pumping action that is based on fluidic impedance differences between different sections of a fluidic conduit. Basically, two or more different conduit sections have different fluidic characteristics or “fluidic impedances”. The fluidic impedance is dependant on the elasticity, size and area of the conduits, among other things.
One of the conduit sections is actuated to change its inner area. The change in area causes a pressure increase in that section. The corresponding pressure increase in other sections is different because of the different fluidic characteristics of those other sections. The pressure difference causes the fluid to flow from the higher pressure area, to the lower pressure area. By continuing to change the fluidic characteristic before the system has an opportunity to return to its equilibrium state, fluid is caused to flow.
The frequency, duty cycle and timing of the pressure increase can be adjusted to change different characteristics of the fluid flow, including speed of fluid flow and direction of fluid flow. Any actuation that can reduce the inner area of a fluidic conduit can be used to actuate the pump.